1UZ ford falcon twin exhaust upgrade from single, recomendations req,

[deankdx]

HI Guys, the single system thread is now possibly irrelavent as there is room for a twin system, i plan to keep the crown manifolds as they are neat and performance is already acceptable(diff gears WERE 2.92 until it blew up 3.45 is to be fitted, performance should be impressive)
so i need advice on what size pipes(still want as much low down torque as i can get) heres a couple of pics to see the space available http://www.lextreme.com/forums/showthread.php?t=2179 look at post 32, i was thinking of keeping 2" from maifolds into cats(spose 2" still? do they restrict flow?) then into X pipe back into main mufflers(want to avoid using resonators if possible but theres room at rear) then out tail pipes all 2" or should this be increased to 2.25? want a good note that i've heard on soarers that "GROWL" for mufflers i was thinking of baffled glass packs?
OR should i keep it a single with the recommended mods in the single exhaust thread

 

[thefastj]

oooh dean your build is souding more and more like mine every day. : )
im running 3.5:1 and stock crown headers also. good choice. lol
so i'm also quite interested in respones to this.

myself am most likely going for the following..

- FULL dual system. no x-pipe, balance pipe, merge AT ALL. sure i may lose a few kW, but it will sound more V8'ie.

- planing on full 2.25" pipes with 2.5" cats...

- mufflers / resonators i have no idea... maybe get the above done first, play with it sounding like a V8 supercar til its ready to be registered and then decide. ; )

 

[Zuffen]

Whilst quality high flow cats cause little restriction I'd be inclined toward 2.25" on a 2" system to allow a little bit of extra breathing.

I'm an avid Autospeed reader and they tend to go .25" over to give a little more capacity.

 

[JBrady]

The key is in the transitions. Straight 2" pipe is fine and will support your power easily BUT if you use marginal transitions this size may become restrictive. 2.25" may be a touch large for optimum but should work very well. Optimum may be 2.125" but this size is not readily available.

Cat size is not critical as the area before and after the core flares. So, the main thing is making certain that the feed and bleed sides are smooth transitions and do not have sharp edges protruding into the flow path. It is OK and in fact desireable to have the feed pipe extend slightly (1/4-1/2") inside the cat and thus creating an anti-reversion transition. The bleed (exit) end of the cat should not have any sharp edges and ideally continue the taper smoothly into the pipe (whatever pipe diameter is used). Of course if you need to purchase cats I recommend the metal substrate type and have provided a link in another thread with that heading.

 

[deankdx]

heres that link thanks JBrady, http://www.rpmoutlet.com/powercat.htm
are these legal and available in australia? would you recomend using full 2" and 2.25" cat?